Real-time optical monitoring of tissue vitality in vivo

Evaluation of tissue O-2 balance (Supply/Demand) could be done by monitoring in real-time 2 out of the 3 components of the tissue O-2 balance equation. In our previous publication (Mayevsky et al. SPIE Vol. 4255:33-39. 2001) we had shown the use of the multiparametric monitoring approach in the neurosurgical operating room. using a device combined of laser Doppler flowmeter (LDF) and surface fluorometer reflectometer. The two instruments having two different light sources', were connected to the tissue via a combined bundle of optical fibers. In order to improve the correlation between tissue blood flow and mitochondrial NADH redox state. the new "Tissue Spectroscope" (TiSpec) that was designed has a single light source and a single bundle of optical fibers. Preliminary results show very clear correlation between TBF and NADH redox state. In addition, the reflected light at the excitation wavelength could be used as an indication for blood volume changes. The results obtained by the TiSpec enabled us to compare tissue O-2 delivery (TBF) with O-2 balance (NADH redox state) in the brain of gerbils and rats exposed toischemia, anoxia and spreading depression. Real-time monitoring of the metabolic state of the tissue has immense potential during surgical procedures.